A generic force measuring device is known from WO 98/56633, which is part of a parking brake, namely an electronic parking brake. To ensure problem-free operation of the parking brake, it is necessary to proportion the force to be transmitted by the Bowden cable exactly, for which it is necessary to determine the transmission of force precisely using the force measuring device. The parking brake has a Bowden cable actuating device which has a motorized drive which moves an actuating element linearly via a gear unit and a threaded spindle in order thus to actuate the Bowden cable connected to the actuating element accordingly. A force measuring device having a housing is assigned to the actuating element. The force measuring device is integrated into the actuating element of the Bowden cable actuating device. However, integration requires corresponding installation space and is moreover costly.
The force measurement takes place at the interface between Bowden cable and the actuating element by means of the force measuring device, which to this end has a force measuring element, designed as a spring. By displacing the actuating element using a motorized drive the spring is correspondingly contracted in accordance with the load on the Bowden cable. The spring deflection is recorded electronically by a position sensor. The characteristic curve of the spring is used to determine the force transmitted by the Bowden cable.
A force measuring device is likewise known from U.S. Pat. No. 6,609,595 B2, which is part of a parking brake, namely a parking brake assembly. Here too the force measuring device is integrated inside an actuating element for the Bowden cable. In this case the force measuring device is installed in a bored hole in the actuating element. The force measuring element is designed as a spring, with the spring deflection being determined using a pusher or a Hall sensor. The load on the Bowden cable can then be inferred from the spring deflection.